The use of vehicles for recreation purposes such as boats, campers and trailers as well as public transportation vehicles such as airplanes, buses and even trains have increased greatly in recent times which in turn has compounded the problem of disposing of human waste created by the people using these vehicles.
Initially some of these vehicles (e.g. boats and trains) disposed of the human waste directly into our environment which, of course, has a tendency to pollute the environment because of the raw sewage disposed therein. Other vehicles (e.g. buses, planes and campers) used holding tanks contained in the vehicles whereby water was used to flush the raw sewage from the toilets and the water and raw sewage disposed of in an appropriate manner as for example dumped into a sewage system. These holding tanks were impractical because they had to be of a relatively large size in order to accommodate the water used for flushing as well as the sewage. Additionally, because the vehicle needed to carry a large amount of water to be used as the flushing fluid this greatly increased the weight. Both defects (i.e. the size and the weight) are of significant disadvantage in, for example, airplanes because of the weight and space involved and in boats, campers and trailers because of the amount of space necessary to accommodate such holding tanks.
In view of the enumereated disadvantages in the prior art sewage disposal systems, most recreational and public vehicles such as boats, planes, trains, buses, etc. are now fitted with so-called recirculating toilets. A recirculating toilet is one which uses a recirculating liquid as a flushing fluid for conveying the human waste from the toilet to a separating tank where the flushing fluid and human waste products are separated. Thereafter, the flushing fluid is recirculated to be used again as the flushing medium. As is apparent, since the flushing liquid is being utilized over and over again only a small amount of liquid is necessary to accomplish its intended purpose (i.e. removing human solid and liquid wastes) thereby enabling a great saving of weight and space which is advantageous in both recreational and public vehicles.
In addition to being used in vehicles, it has been proposed to use recirculating toilets in homes, etc. in order to conserve water and to drastically reduce or eliminate the need for complex and costly centralized sewage treatment plants.
It is now the accepted practice in recirculating toilets, regardless of where they are used, to utilize, as the flushing medium, an oil which is immiscible with liquid human waste (i.e. water). This allows the recirculating fluid or liquid to be separated in, for example, a separating tank, not only from the solid waste material but also from the liquid waste material (e.g. urine).
Even though water immiscible oils have been successfully used as flushing fluids in recirculating toilets, the water immiscible oils possess one distinct disadvantage; the flushing oil gradually acquires a yellow color after being contacted with human waste products. Most people find the yellow color extremely objectionable. Therefore, many flushing fluids have added thereto a coloring agent such as a blue dye which is supposed to mask the yellow color. However, we have found that after very few flushings the flushing fluid still turns yellow even in the presence of color masking agents such as the blue dye mentioned above.
It is thus a desideratum in the art to provide a method and a means for preventing an oil utilized in recirculating toilets from turning yellow for a long period of time by inexpensive and safe methods. However, even though many attempts have been made heretofore, no such system, insofar as we are aware, has been developed.